Testing system



- Jan. 11,1927. 1,613,943

K. M. FETZER TESTING SYSTEM Filed Dsc. 13, 1923 3 Sheets-Sheet 1 yWMM-,my

Jan. 11 1927. 1,613,943

K. M. FETZER TESTING SYSTEM Filed Dec. 13. l 5 Sheets-Sheet 2 1l l l l ll i IIJ 3 Sheets-Sheet 5 IIIIIIIIIIL WANN m Filed Dec. 13

MOA/7g4 sqood by reference to the drawings which, when placed togetherso that itin'. 2 is at the right Figi'. 1 and Fig. 3 is below Fig. 2show a complete testing circuit for makingall necessary tests on tolllines.

Fig. 1, when taken separately, shows the cord circuits ot the precisiontest board. the attendants telephone set. and certain et the equipmentat the niain toll test board.

Fig. 2 shows a inicroainineter, a thernio# couple, and nicans forprotecting these devices against abnormal currents, also a voltineterand a Morse relay, and

Fig. 3 shows a lVheatstone bridge circuit arranged lor mattino; Wellknown toits.

The operation ot the circuits ot this precis'on test` board is asfollows:

Let ns assrnn-e that toll line L has been reported as in trouble. andhas been connected throuejl'i to the precision tei-t board overpatchingcords 11T and 11S and test trunks 119 and 120, and also that thetest nian at the precision test' board has heen notilied accordingly, hyineans not shown.

In ta ring;- up the line 'tor test, the test board attendant will.insert plugT 1251 into jacks 121 and 122 ot' the testing' trunks 119and 120.

TWith all keys in normal position, the at tendants telephone T will newbe connected with the line under test and he can talk with a. lineman ora distant operator if desired. his talkingy circuit can be traced tronithe upper condnetor the toll line L, over the v tip conductors otI cord11T and trank 119,

tip contacts ot jack 121 and the ripper tip Contact oit plus; 123,normal contacts of keys C, el, 8, t3 and 4, through the lc'itdnrndWnclincv ot repeating); coil 12%, and thence back to the lower conductorolf the line L, over keys l, 3, 8, Ll and C, lower tip contactot plire1251, tip springt` ot feel-z and tip conductors ot trunk l and cord 11F.

By throwing liceys (l and to" to the lett and. hey 3 to the right, asonrce o t| talking' battery 138 (Ll-.l volts) is connectel throughV aresistance 126 and the riiht-hand Windings of repcat'ne` ceil 122) tothe line under test. rl`his circuit also peruiits a lineman and thetesti man to talk with each other. talking: battery in this case heine`:aupiilicd to the lineman from the previous test hoard. tt' key C isle't't in normal position. battery can be supplied to the linev undert-cstby thro-Wing;l key S to the right. The test man non' talks throughthe repeating; coil 125.

1tllith key C normal.. ringinig current ol 2t) cycles niay he connectedto the test cord and thence over the trunks 1,19 and ll to the lineunder test by thro-.vine key lt'o itsI left position. ln case key C isthrmyn in its lett position, ringing current can be con-- nected to theline by throwingr key 3 to the left.

To supply cycle ringing current instead ot 2t) cycle, to either ot theabove cou nection, key 10 should be oirierated.

ln case the test inan desires to place a holding tone on the lne undertest in order that the lineman can identity the li'- c and ure it tocall in over, key C niay be thrown to the right whereupon a tonesupplied 'lroin source 127 and interrui'itetl by intern rupter 12S isconnected through transformer 12S) over the right-hand alternatecontacts of key C and the lett-hand nornial contacts of this key to thetip conductors 13b of the plug;` 128, and thence to the line L. Theabove tone o1-cuit is closed by the operation ol relay 130, theol'ieratinn` circuit. tor which is closed at the upper right handalternate contacts ot' relay (l, which circuit is obvious. rlheoperation of key C to the right also connects the secondary side ot thetrans- 't'ornier 129 to the tip and ringcoinlucttnJz-i ot the cord.Relay 181 which is connected across a condenser in the secondarywinding; ot ranslornier 129 now bridged across the cord and trunk, andwill be op crated by ringing' current coniingr in oi'er the testing,Ttrunks and thc cord troni the toll line caused., for example, by alineman ringing` on the line with his test' set. Relay 131 in operating,locks up in a circuit which inay he trace/l from battery, through thelett hand Winding;- and lett hand alternate contacts of this relay` andthe lett hand alternate contacts oit relay 1B() through aut;- iliz ysignals to ground. Under this condition, lanip 132 will. be liohted.When the test hoard attendant answers such a call, he restores key C tonorinal thereby releasing` relays 13() and 131. and eXtinyjuishinel lamp132 'lfhe Voltage ot the test buttery Elli?) measured by thro\.\i1u` heylo the which short circuits resistance 2511: normally connected inseriez with the test battery and also short' circuits the tip andrinoconducH tors 135 :intl l-lt of the testing;` cord. The Yoltnieter2-3'? is now comici-ted directif.' across the terminals ot the testbattery in a` circuit which can be traced 'liroln the positive terminalol the test battery over the normal contacts oi" key 5. the nornialcontacts et .keys 12, t5, 13, 21. t? und l. alternate contacts of key(t, norrual contacts oit keys T. 1, (i, 23. 13 and tl. upper and lowerinner normal contacts 0ll relay lt, normal coin tarts ot keys l2 and i2.rolL ieter 3'?. norniril contacts oli' keys 12. 1l- :irul it. alternatecmitacts oli lie. tt, and normal contacts o'l" key 5 to the negativeterminal oit battery 233,.

Foreign potentials iur-,onliney over the test trunks 119 and 124,1 canbe measured by throwiircY keys C and 5 to the lett which disconnects thetest battery 233 and connects can l richt llt? the voltmeter nl directlyacross the conductors lilo and i235 ol' the cord in such a manner thatthe incomingl foreign potential will be registered on the voltnieter.linder the conditions existir.;y with keys tl and il thrown to the lett,the )ositive terminal ol the voltmeter 223i will be connected to thering conductor 13:3 et the cord. ln 'ase the voltmeter should show abackward reading, key (3 may be thrown lo the left, theieby reversing,Ythe conductors to the voltmeler.

toreign potential between the tip ol: the line and `ground or betweenthe ring conductor ot the line and ground may be .tear-aired by throwingkey l either to the ight oi the lett depending on whether the tip .rring ot' the line is to be tested to `ground, C and beine' thrown to thelet't as betere. vUnder either ot' these conditions, the positiveterminal ot the voltmeter will be connected to the conductor under 'lesta nl the negative terminal will be connected to ground. ln ease it isdesired to reverse the voltnieer connection. key (S may be oprated tothe lel't as bei'ore.

l` test lor the continuity ol' the line L under test, the key C isthrown to the le'lt which connects the battery 2323, the resistance L3and the voltmeter 23T in series across the tip and ringl ot the line. lnmaking' this test, it the circuit is open, a momentary deflection ot thevoltmeter needle will sometimes be obtained, especially il. the line unter test is a long one and its insulation resistance high.

ln testine toll lines that hare b'idged electromagnetic devicesconnected across them at the distant end, the presence otl thisapparatus will be indicated by a steady deflection ot' the voltmete assoon as the test key C is tlnown. However, itl such devices include aserie.l (anulenser, the voltmeter ne alle will he detlected onlymomentarily.

(in short lines, the presence ot bridged electromagnetic appa atus canalways be determined by operating;l key t3 to the lett which will ausethe voltmeter to be detleced by the disclu ree ot' the crmdenser at thedistant end, the magnitude oit the dc- `Flection being a rough estimateot the canacity bri tired across the line. (En long lines having' morethan one bride'e ot this sort or on cable circuitsr` this deflection maybe too large to be accurately read on the voltineter. ln such caes. heyL should be operated o the lett, thereby reduci in the de llection byshunting resistance Q'Jt) across the voltmeter terminals.

'The tes'Y tor `grounds on the line li is similar to the test 'torcontinuity except that key l i: also used. TVith key C tlnown to thelet't` tae operation ot key l to the lett opens the tip side 136 ot thetesting' circuit and connects the po=itiye terminal ot' the battery 23?to ground. The operation of key l to the right opens the ring side 1535ot the testing circuit and connects the posiA tive terminal ot thebattery to lground. ln either case, the voltmeter readingwill be anapproximate indication el the resistance ot the connected side olj thecircuiti to ground. 'l`he line under test must be opened at the distantend to determine by these tests il the ground is on the tip or the ringconductor. rl`he approximate resistance tor either oll the voltnietertests lun'einbet'ore de scribed 'an be readily computed by a well knownAtolmuh which is based upon the tact that the scale divisions trom 71 roto the needle ol the voltmeter represent the resistance ot tacvoltinctcr and that the scale divisions `from the needle tothe batteryvoltage represent the resistance in serie.; with the voltuieter. 'thisYlm'mula is c.\

where 2 Xzzzthe unknown lesistance under test,

rrthey resistance otl the voltmeter,

itl: he test battery voltage measured as betere describeti VDzthevoltmeter reading` when in series with the resistance to be measured,

rzthe resistance (QSL) in series with the testing' battery.

ln practice. the resistance ol: the voltmeter used 'tor these tests maybe either ltltljtitlt) or 1.000 ohms depending on whether the voltmeteris connected in the circuit directif; or whether the voltxneter shunt22E!) is connected by operating;- key 2 to the lei't.

In measuring resistances with the Voltmeter, the results are more acculate when the resistance ot the voitmeter is nearly equal to theresistance being measured. For this reason key 2 should be operated tothe lett to connect the shunt 23S) across the voltmeter when ine-asuingr resistances up to 10.000 ohms. Assuming' that the battery L33stands at 150 volts, it' the voltmeter riads in excess ol 135 volts,with key 2 in its normal position, the resistance K is about 10,00()ohms or less and the shunt should therefore be used by operating' key ilto the lett.

'l`he insulation resistance ot the line can be determined either by thecontinuity testl or test t'or ground previously described` but since theinsulation resistance ol a line is. in gene al, much higher than theresistance r (2B-l) in series with the testineY battery which in theassumed iase is 500 ohms, this resistance an be disregarded. Further thekey 2 should not be thrown to connect the shunt 239 across thevoltineter terminals in order that the resistance l the voltlneter willbe as high as possible, that is, as close as possible to the resistanceto be measured.

CJI

and as this bridge circuit and the various tests niadc therewith tornino part ot' the present invention it is not proposed to dcscribe themt'urther. other than to point out that key BK controls the supp y otcurrent from the potentiometer B-l-T to the points T an'l C ol thebridge and the key GK controls the connection ot the galvanonieter tothe points R and JJ ot' the bridge and that the, various well knowntests, as before mentioned, are made by Varying the resistance ot thevariable arms A, B and R in the bridge 342, by adjusting thepotentiometer 34T and the Variable galvanometer shunt and by actuatinglthe keys BK and GK as is well understood to those skilled in the art.

Altermztz'ng current lVzeatstone bridge tests.

It will be noted that the galvanometer 343 can be used tor either director alternating current measurelnents, no pole changing device beingrequired when used with alternating current. .For the purpose o't'making capacity tests 't'or locating breaks in the line and also formeasuring the capacity ot condensers, etc., the present testing circuitis so arranged that, by substituting eight cycle alternating currentsupplied by the generator (l through the filter F, 't'or the 150 voltdirect current testing battery 233, t'or energizing the tield Winding ofthe gah'anometer and as a source ot bridge supply, such tests can bequickly and easily made.

When a break occurs in a line wire or cable conductor and the endsremain 1nsulatied troni the other wires on ground, a capacity testy isthe only means olf locating the break. rl`his test. is made with a.standard condenser ot known capacity and can be briefly described astollows: 'l`o determine the distributed capacity ot one wire ot the lineto ground the single plug 13u associated with the ring conductor ot thetest cord is plugged into the jack corresponding with the wire to bemeasured and the other single plug 13T is plugged into the jack 3523.Keys C, 123, l-tand l are then thrown to the lett and key 1G is thrownto the right. The bridge is now connected tor the well known Murray testand eight cycle alternating current 'trom the generator (il is suppliedthrough the tilter F to the teld winding ot the galvanonieter and to thepotentiometer l-li by reason ot the operation ot' relay Bitti, when key15 was operated. lt will be noted that the operation ot key 15 alsooperated relay 35i which closed the circuit for motor 355 to drive theeight cycle generator Gr.

Vire now have esentially an arrangement tor comparing the capacitybetween the open wire and ground with the capacity ot' the standard onemicrot'arad condenser 356. In

this arrangement the arm A ot the bridge is set at 1000 and the lt arm,which is to be varied. 'torni two arml of thc iilurray connection andthe open wire and the grounded condenser 356 toria the other two arms.By adjusting the R arm until no current tlows through the galranometerwhen keys till( and BK are depressed, the re listances in arms A and lare inversely proportional to the capacities ot' the line and thecondenser, which may be expressed as follows:-

Where:

Czthe capacity in microtarads ot the grounded condenser 356,

O ,rthe distributed capacity in microlarads between the open line wireand ground.

A=the 1000 ohms in the A arm ot the bridge, and

Rzthe. resistance in the R arm ot' the bridge.

Since the arm A has been set at 1000 and the standard condenser Z350 isone microtarad, the above formula may be simplitied as 'follows-n It is,ot course, understood by those skilled in the art that Vt'or the purposeot locating the break in the line it is necessary to determine or tohave previously determined the, electrostatic capacity per unit otlength ot the line under test or ot one having similar characteristics.

ln case it is desired to measure the mutual capacity o1 a pair ot wires,the same keys are operated and the two plugs '13S and 13? are insertedin the same jacks as in the preceding test and in addition a singleconductor patching cord is used to patch hetwcen thel other trunk jackand jack 357. Under this condition the alternating current supplied tothe bridge is disconnected from ground and connected to the point 'l otthe bridge instead, the capacity between the wires ot the pair thenconstituting.; the X arm oli the bridge. Thel preceding lormula alsoapplies in this case wherein (l: is now the mutual capacity oll the pairol wires instead ol the grounded capacity ot one wire.

1n case it is desired to measure the :apacity ot condcnsers and otherapparatus otf a similar nature, a two-conductor plug and cord (notshown) is employed, the strands ot this cord being connected to thecondenser to be tested. In making this test the plug 13S o'lE thetesting cord is plugged into the jack 3:38 and the plugl 13T is pluggedinto the jack 853.

The plug end ot the two-conductor cord associated with the condenser tobe tested is now inserted in jack 350. its in the case ot' measuring theline capacity, the keys C, 13, 1st and are operated to the lett and key16 is oljierated to "the right thus establishing the ltiurray bridgeconnection and connecting eight circle current lo the liotentninielerand galrauorietcr `field coil as. hc'lore described. i'i'ients are madeas in the crise betere men-- tioned, the condenser under test lieiing),`inert ly substituted for the open wire in the X arm of the bridge.

The H arm et the Ttithe-ratstone bridge be isolated 'troni the otherbridgfje arms connected in series with the tip and r conductors of thetesting cord circuit throufing ley 1&3 to the right. lilith ths arm oithe bridge connected to the testing cord in the above manner. it can beinserted in an external circuit by throwing` lrcj-,f C to the lett andinfiiertng the pings 153i' and lilo in any desired jacks.

,ll/cusweimar of sim/ZZ (fur/fwrite.

t is soi'netinics desired to measure alter nat'ing` current ot' theorder ot ore-lultl niilliampere to .titty niiliiamperefi and` t. rectcurrent ot the order ot troni one n'iieroampere to titty miilian'iperesincoming over the line, or, to measure the current supplied to theiVheatstone bridge while a bridge measurement is in progress and. alsoto inea, ure niiscellaneous small external currents. For this purpose athermo-couple 201 and a micro-ammeter 202 are provided. Either direct oralternating current can be measured by using` the thermo-couple andniieroainmeter, together but direct current only can be measured withthe micro-annneter alone.

A. Variable so arranged that upon the operation o't' l: y 12 to thelett, the shunt is associated with the lnicro-ainnieter and by operatingthe key 12 to the right it is associated Awith the thermo-couple.

ln accordance with iteature ot the invention means including thisvariable shunt are provided and so arranged lthat the thermocouple andmicro-a1nnieter are protected from excessive currents until the test manhas an opportunity to detern'iine its approxiniate strength.

A description ot this feature now follows zn Let it be assumed that itis desired to measure current flowing in the line L and, therefore,testing cord plug 123 is inserted in jaclts 121 and 122, key C is thrownto the lett and key 12 thrown to the right. The operation ot lfey 12connects ground at its contacts 207 to operate re1 y S38, the circuit`for which can be traced trom battery, winding oi' relay 338, innerupper normal contacts of key 14, right-hand uppermost normal shunt 200also proridcd and contacts ot key 13, contacts 211 ot key 12 and toground over contacts 207 ot the saine key. Relay 338, in operating,connects the R arm of the lilheatstone bridge 342 and the heatingelement lil ot the thern'io-couple 201 in series across the tip and ringo't the line. This circuit can be traced 'trom the ring con ductor 135oi the plug 122i, upper alternate contacts ot key C, lower normalcontufts ot keys 7, l, and 3, lett and right inner upper normal contactsot hey 13, left-hand lower normal contacts ot key 8, lower inneralteri'iate contacts otl relay 338, the R arin oi bridge 3&2, upperinner alternate contac ot relay 5538, lettdiand inner lower normal contacts ot key 12, right-hand inner lower alternate contacts ot key 12,no1-mal contacts ot jack 200, heating element H of the thermo-couple201, normal. contacts ot jack S, rightdiand inner upper alternatecontacts ot hey 12, left-hand inner upper normal contacts ot key 12,lett-hand inner upper noriiial contacts ot key 0, right-lured inncrlower normal contacts o't key 13, right and lett inner lower normalcontacts ot key 13 and upper normal contacts et keys i3, 6, 1 and 7 andlett-hand lower alternate contacts ot keys C to tip conductor 1.30 oithe test cord plug 123. The operation ot key 12 also dis connected the150 volt test battery 23? and the rolt meter 2ST. lt should be notedhowever, that at this time, the heating element H ot the thermo-couple201 is short-circuited at the uppermost and lowermost normal contacts ofrelay 205 thereby preventing any current flow therein which might behigh enough to burn it out.

Now, it the contact arm of the rheostat 200 is not in the Zero position,it should be turned to this position thereby closing contacts 210 tooperate relay 205 in an obvious circuit. Relay 205, in operating, locksup through contacts 20T -o't key 12 to ground and removes the shortcircuit around the heating element H of the thermo-couple. Relay 205, inoperating, also connects ground at its inner upper alternate contactsfor operating relay 203 which relay in operating breaks at its uppermostand lowermost normal contacts a shortcircuit, which up to this time hasexisted across the terminals ot' the inicroannneter 202.

It will be noted, however, that the heating element H ot thethermo-couple 201 is still short-circuited by the contact arm ofrheostat 20G while it remains in the zero position, and the next opeation, therefore, is to adjust this arm to any desired value ot shuntaround the thermo-.couple heating element. lt will be noted that thisshunt can be re moved entirely by throwing the rhcostat arm to theextreme right which is its open position.

it is, of course, understood that variable resistance arin R ot thebridge can loe till to control the current regulated as desiredthern'io-couple heating flowing through the element.

It direct current ol less than one-halt milliainpere is to be measured,the microanuneter Q92 can be used alone without the thermo-couple. Toestablish this connection key 12 is thrown to the lett instead ot to theright, whereupon relay $38 is operated as betere Yfrom ground at thelett-hand lowermost alternate contacts ot key 12, and relay 204 isoperated troni ground at contaets 212 of this key. rthe operation otrelay 338 in conjunction with key 12 in its le'lthand operated position,connects the microammeter Q02 and Ythe resistance arm R ot bridge 3l@ inseries across the tip and ring ot' the testing cord. As in the previouscase, however, micro-annneter 202 is short-circuited at the upper andlowermost normal contacts of relay 293. rl`he operation ot relay 20-ldisconnects the rheestat 20G from the thermo-couple 201 and connects itacross the terminals ol' the micro-animeter i202 and disconnects the Gelement ot the thermoconple 201 Yfrom the miero-annneter. rlhis circuitcan be traced 'from the zero contact o'tl the rheostat, inner loweralternate contacts ot' relay QO-l to the negative terminal ot' theinicro-auuneter and from the rheostat arm over the upper inner alternateconi acts ot relay QO-l to the positive terminal o t the microan'nneter.The short circuit across the terminals of the micro-annneter is removedas betore by the operation ol relay 203 which is cimtrolled by relay205, which in turn is operated when the rheostat arm is rotated into itsZero position thus closing contacts 210. Ytelay Q03, in operating, locksup to ground over its inner lower alternate contacts and the lett-handuppermost alternate contacts ot key 12. As in the case otl thethermo-couple, the micro-ammeter is now short circuited by therhcostatarm until the test man adjusts the resistance ot the shuntacross the micro-annueler to the desired value.

Vin case it is desired to malsurc alternating currents supplied lo theYvheatstone bridge while a bridge measurement is in progress1 it isnecessary to use a patching cord, not shown, one end ot which isequipped with two singley conductor plugs and the other end with adouble coiuluclor plug.

lilith the connections set up Vl'or any ol the previously describedYi'heatstonc bridge tests. the double conductor plug ot' the putt-bine'cord is inserted in jack SGO and the two single conductor plugs areinserted in jacks 20S andL 209. Then it key 12 is thrown to the rightand the arm ol rheostat MG is rotated to the Zero position, relays Q05and 20?, operate in succession to remove the shunt around thethermo-couple 201 and the micro-aimneter Q02 as previously described.rl`he current supplied to the lVlieatstone bridge at points C now llowsthrough the parallel paths formed by the heating element lil of thetl'iermo-couple 201 and whatever resistance is in the rheostat 206 and areading of the total current will be indicated on the inicro-ammeter202, the micro-animeter being calibrated tor each value o't resistancein the rheostat.

In case it is desired to determine the eurrent in the X-arm ol? thebridge, the saine connections are set up except that the two conductorplug ot' the patching cord is inserted in jack 350 instead ot' in jack360.

In case it desired to read direct current supplied to the bridge or inthe X-arm otl the bridge, it this current is less than onehallmilliainperes, the micro-amn'ieter can be used alone as be toredescribed. To establish this connection` key 1Q is thrown to the let'tinstead otl to the right, the plug 123 is inserted in jacks 2123 and 21%instead of in jacks 20S and 2th), and the two conductor plug ot thebetere mentioned patching cord inserted in either jack SGO or 235()depending upon whether the current supplied to the bridge or in theX-arni is to be measured.

lt will be observed from the foregoing that the micro-anuneter andthermo-couple are protected from excessive currents by means olf ashort-circuit across their terminals which is only removed when thecontact arm ot the rhcostat is moved into its r/,ero position, thereuponremoving the lirst short circuit and substituting another whichiiufludesv the contact arm and zero terminal o' the rheoslat.

'lhc test man now, therefore, has control ol' the amount o'lE currentwhich passes through these devices and can adjust the contact arm asdesired, even to the extent ot throwing it to the open position, therebyremoving the shunt entirely in case the micro-anuncter indicates tha|`the 'full current in the line is not great enough to damage eitherdevice.

ll'hat is claimed is:

'1. An electrical. device` means tor short circuiting said device, avariable resistance shunt circuit adapted to be associated therewith,vand means operated in response to reduction o't' the resistance in saidshunt circuit to a minimum value vl'or removing said short circuit andlor substituting said shunt circuit.

2. ln combination, an electromagnetic relay` a sensitive. electricaldevice, a variable resistance in shunt to the terminals thereof. saidvariable resistance including a movable contact. another low resistanceshunt circuit tor said device completed by the normal contacts ot' saidelectromagnetic relay` and a circuit tor said relay completed when saidmovable contact is in a predetermined position, whereby Said lowresistance shunt circuit is interrupted.

3. In combination, a device for measuring elecxzrienl Current flow, ashort Circuit being' normally connected across the terminals of Suiddevice, means for opening the said short eirenip4 e. rheostzxi having':1, movable Contact adapted lo he associated with Suid device,

and means including the movable Contact of said rheostat for actuatingsaid first means and for operatively associating Said rheo- Stat withsaid device.

ln Witness whereof, I hereunto Subscribe my nume This 11 dmv oiADer-einher A. l). 1923.

KARL M, FETZER.

